SNCA and Parkinson disease: However, in chronic neurodegenerative diseases, persistent stimuli—such as amyloid-β accumulation in Alzheimer’s disease or α-synuclein aggregates in Parkinson’s disease—prolong microglial activation, leading to sustained production of pro-inflammatory mediators like tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β).